Short-Lived Climate Forcers in the Arctic the Importance of Monitoring. Andreas Stohl Norwegian Institute for Air Research

Transcription

1 Short-Lived Climate Forcers in the Arctic the Importance of Monitoring Andreas Stohl Norwegian Institute for Air Research

2 Why are we interested in Short-Lived Climate Forcers (SLCFs)? Contribute to global warming/cooling and deteriorate air quality. Possible synergies between climate policy and air quality policy (warming pollutants like black carbon). But there may also be trade-offs between climate policy and air quality policy (cooling pollutants like sulfate). Aggressive SLCF mitigation could reduce Arctic temperature increase by about 0.5 C. 2

3 What are SLCFs? And what are their lifetimes? Long-Lived Greenhouse Gas: Carbon dioxide order of 100 years SLCF?: Methane SLCF: Ozone Aerosols ca. 9 years weeks to months days to weeks 3

4 Forcing mechanisms of aerosols (especially BC) in the Arctic

5 Recent focus on Black Carbon (BC) BC is an absorbing aerosol A component of soot, produced by combustion processes Large anthropogenic sources Pollutes both atmosphere and cryosphere (albedo reduction) Few emission sources in the Arctic but long-range transport from outside High BC concentrations observed in the Arctic during «Arctic Haze» Model simulations very uncertain. Results are extremely sensitive to scavenging parameterizations (BC lifetime) and to uncertain BC emission sources at the very highest latitudes (Russia!). 5

6 Model problems ca. 10 years ago From: Shindell et al. (2008) 6

7 - Models more accurate now, but still substantial problems. - Are models more correct now, or are they just better «tuned»? - Importance of multi-site evaluation -> Svalbard one component. Eckhardt et al.,

8 Emission sources of BC highly uncertain Emissions in Russia particularly uncertain. Flaring discovered as an important emission source in Russia. But the relative magnitude of flaring emissions under discussion. 8

9 Annual-mean BC surface concentrations simulated with FLEXPART (total, left; relative flaring contribution, right) Stohl et al. (2013) Flaring emissions (ECLIPSE) Flaring emissions contribute 42% to Arctic-mean BC surface concentrations! (52% in January!) 9

10 Detailed look at Zeppelin timeseries Stohl et al., 2013 No increase in measured CO, consistent with high BC/CO emission ratio of flaring 10

11 Another inventory (higher flaring emissions), another model (CMAQ). Huang and Fu, 2016 However, other gas flaring emission estimates are lower than ECLIPSE. Isotopic measurements do not support flaring as an important BC source. 11

12 Local sources of BC also important BC concentrations at Zeppelin (Ny Ålesund) under stagnant conditions in summer when cruise ships are in the fjord: 10.3 ng/m 3 Without cruise ships: 8.0 ng/m 3 Eckhardt et al. (2013) 12

13 Trends of BC Strong downward winter trends in the 1990s explained with the collapse of the economy in Eastern bloc countries (Sharma et al., 2014; AMAP, 2015) However, increase of BC in an ice core from Holtedahlfonna (Ruppel et al., 2014) 13

14 Has dust been overlooked? Radiative forcing in the Arctic similar to BC. Like BC, strong albedo effect. Extensive dust storms documented for Iceland. Dust «natural», but sources influenced by climate change

15 Dust storms have been documented also on Svalbard (e.g., Dörnbrack et al., 2010). Mobilized coal dust represents an anthropogenic source. There exists no long-term monitoring of dust on Svalbard. How important is it? Dust storm and loess accumulation, Adventdalen, Svalbard 15

16 Dust global models lack the Arctic 90 N 60 N?????????????????????????????????????????????????????????? Engelstaedter & Washington, S 90 S??????????????????????????????????????????????????????????

17 New simulation of dust emissions and dust transport, considering high-latitude sources Groot Zwaaftink et al. (2016) Landcover data GLCNMO2 & high-resolution map Iceland FAO Sand & clay maps Meteorological data from ECMWF operational analysis fields Simulating years

18 Dust concentration vertical distribution per latitude Winter (DJF) Summer (JJA) Latitude Latitude Latitude

19 Contribution of different dust source regions to Arctic dust Arctic atmospheric dust load Arctic dust deposition

20 Radiative forcing by dust in the Arctic Kylling et al., 2017, submitted to GRL based on dust simulations by Groot Zwaaftink et al. (2016) Mean: 0.43 W/m 2 Remote dust sources (Asian, African deserts) most important for Top-of-Atmosphere (TOA) forcing. Local dust sources (>60 N) most important for Bottom-of-Atmosphere (BOA) forcing. Albedo reduction of snow/ice dominates BOA forcing. For comparison: Arctic TOA RF due to BC: Cryosphere: 0.17 W/m 2 Atmosphere: 0.38±0.30 W/m 2 (Quinn et al., 2015) Mean: 0.21 W/m 2

21 Radiative forcing efficiency Kylling et al., 2017, submitted to GRL based on dust simulations by Groot Zwaaftink et al. (2016) Local dust sources (>60 N) are orders of magnitude more efficient in terms of radiative forcing than remote sources, both for TOA and BOA forcing.

22 Methane Important «natural» emissions (wetlands). Thawing of permafrost important issue. ppb v Zeppelin CH 4 Feedback to climate change substantial. Changes in global concentrations poorly understood; thus, future projections also very uncertain. 22

23 Inverse modelling to determine emissions Important to «verify» bottom-up emission inventories. Thompson et al., 2017 But relies on a dense observation network. Svalbard one important component, but not more! 23

24 High-latitude methane emissions Thompson et al., 2017 Posterior methane emissions Difference to prior methane emissions Much higher methane emissions in the Western Siberian lowlands and in Alberta, Canada. Alberta signal is clearly of anthropogenic origin (oil sands). Substantial year-to-year variability of emissions in Siberian Lowlands and Hudson Bay Lowlands are correlated with air/soil temperatures.

25 Conclusions SLCFs are an important but poorly quantified component in Arctic warming. High-latitude dust has been «understudied» relative to BC. Substantial gap in the monitoring network! Atmospheric monitoring on Svalbard is important, as one of only few Arctic sites. Sensitivity to emissions in Russia a particular «bonus». The largest value of Svalbard monitoring comes through integration into the global network. Svalbard-centric research not a particularly effective strategy. 25